Time filter

Source Type

Liang J.,Huizhou University | Xu B.,North China University of Water Conservancy and Electric Power | Cai Z.,Air force Radar Academy
Journal of the Optical Society of America B: Optical Physics | Year: 2011

Internal modes and internal oscillation of necklace solitons in Bessel photonic lattices imprinted in selfdefocusing and self-focusing materials are investigated. Under the same parameters, necklace solitons in selffocusing material possess larger power than that of self-defocusing material, and the stability of solitons in defocusing material is better than in focusing material. It is shown that the internal modes have both real and imaginary parts in such cases, differing from the one-dimensional case. While white noise gives rise to jitter of the intensity of stable necklace solitons, the stable solitons perform long-distance and quasi-periodic oscillation of intensity and shape under the perturbation of internal modes, and the solitons in self-defocusing material experience larger oscillation amplitude than that in self-focusing material. © 2010 Optical Society of America.

Xu J.,Air force Radar Academy | Yu J.,Tsinghua University | Peng Y.-N.,Tsinghua University | Xia X.-G.,University of Delaware
IEEE Transactions on Aerospace and Electronic Systems | Year: 2011

Based on the coupling relationship among radial velocity, range walk, and Doppler frequency of the moving target's echoes, a novel method is proposed, i.e., Radon-Fourier transform (RFT), to realize the long-time coherent integration for radar target detection. The RFT realizes the echoes spatial-temporal decoupling via joint searching along range and velocity directions, as well as the successive coherent integration via the Doppler filter bank. Besides, four equivalent RFTs are obtained with respect to the different searching parameters. Furthermore, a generalized form of RFT, i.e., generalized Radon-Fourier transform (GRFT), is also defined for target detection with arbitrary parameterized motion. Due to the similarity between the RFT and the well-known moving target detection (MTD) method, this paper provides detailed comparisons between them on five aspects, i.e., coherent integration time, filter bank structure, blind speed response, detection performance, and computational complexity. It is shown that MTD is actually a special case of RFT and RFT is a kind of generalized Doppler filter bank processing for targets with across range unit (ARU) range walk. Finally, numerical experiments are provided to demonstrate the equivalence among four kinds of RFTs. Also, it is shown that the RFT may obtain the coherent integration gain in the different noisy background and the target's blind speed effect may be effectively suppressed. In the meantime, both the weak target detection performance and the radar coverage of high-speed targets may be significantly improved via RFT without change of the radar hardware system. © 2006 IEEE.

Xu J.,Tsinghua University | Xu J.,Air force Radar Academy | Zuo Y.,Tsinghua University | Xia B.,Tsinghua University | And 3 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2012

For along-track multichannel synthetic aperture radar, this paper proposes a novel ground moving target signal model in the high-resolution complex image domain. Based on the range-Doppler imaging of static scene, the 2-D complex response of an isolated rectilinearly moving target is derived via the stationary phase principle (SPP) approximations. It is shown that moving targets in complex domain can be divided into three types according to the 2-D motion distribution and the SPP approximation conditions. Different from the known peaklike response of a static target, different amplitude and phase modulations will appear for different types of moving targets. Moreover, a single target can be split into two targets in the image when its Doppler spectrum spreads over two ambiguous Doppler zones. All types of targets will have the same Doppler interferometric effect along multichannel images, which is decided by the target's ambiguous Doppler frequency. Furthermore, with the proposed signal model, the complex image properties can be completely described and analyzed. Finally, some numerical experiments are also provided to demonstrate the effectiveness of the proposed signal model and analysis. © 2006 IEEE.

Nie T.,Air force Radar Academy | Sheng W.,Air force Radar Academy
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2010

Supply support optimizing is an important approach to improve operational readiness and reduce life cycle cost for equipments. Through analyzing the two-echelon supply support system for repairable spare parts of complex equipment, and researching the relationship of spare parts support and operational readiness, a supply support optimizing model is proposed, which chooses system supply availability as the object and the total acquisition cost as the subject. Marginal efficiency analysis algorithm is applied to achieve the optimization. Finally, several examples are given to verify that this model can optimize spare parts storage, and evaluate the effects on support efficiency of some important factors, including different stock, repair capacity of two levels, reliability and so on.

Chen Y.,Air force Radar Academy | Xia M.,Air force Radar Academy | Zhu Z.,Air force Radar Academy
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

Aiming at the problems of traditional photovoltaic grid-connected system structure, a new type of photovoltaic grid-connected cascaded inverter scheme with stepped waveforms and instantaneous value feedback hybrid control. In this method, one part of the cascaded units use stepped waveforms control, the other part use octave sinusoidal pulse width modulation (SPWM) control with instantaneous current feedback. The output voltage comes from the two parts in series. The analysis of the output voltage harmonic shows that the amplitude of the output voltage and the power factor can be adjusted by the SPWM wave phase-shift angles; the low order harmonic of the output voltage is aroused by the stepped waveforms control part, which is the theoretic background for the output filter design. A simple algorithm for the trigger angles of the stepped waveforms modulated inverter is proposed, which is not only fit for the cascaded inverter with different voltage steps, but also fit for online calculation. The experimental results show that this scheme has simple structure, high reliability and low switching loss.

Ren J.,Air force Radar Academy
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

To further research the multifractality of sea clutter, multifractality of IPIX radar sea clutter has been analyzed by Qth-order Moment Structure Partiction Function (Q-MSPF) method in detail in this paper, through simulation analysis, two target detection methods based on analysis of the mass exponent function and the source of multifractality are proposed, and proved to be effective. © 2011 IEEE.

Xiao L.,Air force Radar Academy | Guo L.,Air force Radar Academy
CCTAE 2010 - 2010 International Conference on Computer and Communication Technologies in Agriculture Engineering | Year: 2010

Based on the analysis of the development of agricultural mechanization, the trend of agricultural service system reform, agricultural environment protection and the development of information technology, it is possible to realize the precision agriculture. This paper designs the agricultural environmental monitoring system based on the wireless sensor network (WSN). The system can real-timely monitor agriculture environmental information, such as the temperature, humidity, and light intensity. This paper introduces the theory of the monitoring system, and discusses the aspect of hardware and software design of the composed modules, network topology, network communication protocol and the present challenges. Experiments show that the node can achieve agricultural environmental information collection and transmission. The system has the feature of compact in frame, light in weight, steady in performance and facilitated in operation. It greatly improves the agricultural production efficiency and automatic level drastically. © 2010 IEEE.

Liu J.,Huazhong University of Science and Technology | Liu J.,Mechanical Engineering Institute | Wu C.,Air force Radar Academy | Liu W.,Huazhong University of Science and Technology
Decision Support Systems | Year: 2013

Recommendation systems have received great attention for their commercial value in today's online business world. However, most recommendation systems encounter the data sparsity problem and the cold-start problem. To improve recommendation accuracy in this circumstance, additional sources of information about the users and items should be incorporated in recommendation systems. In this paper, we modify the model in Bayesian Probabilistic Matrix Factorization, and propose two recommendation approaches fusing social relations and item contents with user ratings in a novel way. The proposed approach is computationally efficient and can be applied to trust-aware or content-aware recommendation systems with very large dataset. Experimental results on three real world datasets show that our method gets more accurate recommendation results with faster converging speed than other matrix factorization based methods. We also verify our method in cold-start settings, and our method gets more accurate recommendation results than the compared approaches. © 2013 Elsevier B.V.

Ma N.,Air force Radar Academy
Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition) | Year: 2010

The system could not give full play to its performances, because multiple network cards and multiple connections technology in iSCSI can not appropriately assign every task of the system. Thus, a dynamic load balancing algorithm using a feedback control mechanism is proposed to improve the whole performance in iSCSI system. This algorithm adopts a feedback technology, collects much resource states in the whole system, and calculates the real-time feedback's value, combines the previous feedback's value to assign every system's task in order to dynamically adjust the system's load state. The test results show that the performance is improved with this algorithm.

Sheng W.,Air force Radar Academy | Ren J.,Air force Radar Academy
Dianbo Kexue Xuebao/Chinese Journal of Radio Science | Year: 2011

Multifractal theory is introduced for modeling HF radar sea clutter, and a new time-domain model based on multifractal for HF sea clutter is presented. Simulation analysis indicates that the multifractal model has a similar multifractality with real sea clutter data by comparison among multifractal model, real sea clutter data and Fractional Brownian Motion(FBM) model. In addition, by using probability density function comparison analysis among 3 most commonly used distributions such as Weibull, Log-Normal and Rayleigh distribution, and through a statistical test by modified Kolmogorov- Smirnov(K-S), the conclusion of the proposed multifractal model of HF radar sea clutter possesses the apriori statistical characteristics is obtained, which further proves that this time-domain multifractal model for HF radar sea clutter is quite reasonable and effective. © 2011 by Editorial Department of Chinese Journal of Radio Science.

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